Understanding the Earth’s geological nitrogen (N) and carbon (C) cycles is fundamental for assessing the distribution of these volatiles between solid Earth (core, mantle and crust), oceans and atmosphere. This Special Communication about the Earth’s N and C cycles contains material that is relevant for researchers who are interested in the Topical Collection on planetary evolution “Reading Terrestrial Planet Evolution in Isotopes and Element Measurements”. Variations in the fluxes of N and C between these major reservoirs through geological time influenced the evolution and determined the unique composition of the Earth’s atmosphere. Here we review several key geological aspects of the N and C cycles of which our understanding has significantly advanced during the last decade through field-based, experimental and theoretical studies. Subduction zones are the most important pathway of both N and C from the Earth’s surface into the deep Earth. A key question in the flux quantification is how much of the volatile elements is stored in the downgoing slab and introduced into the mantle and how much is returned back to the surface and the atmosphere through arc magmatism. For N, the retention of N as \(\text{NH}_{4}^{+}\) in minerals has a major influence on fluxes between reservoirs. The temperature-dependent stability of \(\text{NH}_{4}^{+}\)-bearing minerals determines whether N is predominantly retained in the slab to mantle depths (in subduction zones with a low geothermal gradient) or devolatilized (in subduction zones with a high geothermal gradient). Several lines of evidence suggest that the mantle is regassing with respect to N due to a net influx of subducted N over time, but this issue is highly debated and evidence to the contrary also exists. Nevertheless, there is consensus that the majority of the planetary N budget is stored in the Earth’s mantle, with the continental crust also constituting a significant N reservoir. For C, release from the subducting slab occurs through decarbonation reactions, dissolution and formation of carbonatitic liquids, but reprecipitation of C in the slab or the forearc mantle wedge may limit the effectiveness of direct return of C into the atmosphere. Carbon release through regional metamorphism in collision zone orogens also has potentially profound effects on C release into the atmosphere and consensus has emerged that such orogens are sources rather than sinks of atmospheric CO₂. On shorter timescales, contact metamorphism through interaction of mantle-derived magmas with C-bearing country rocks, and the resulting release of large quantities of CH₄ and/or CO₂, has been linked to global warming events.

了解地球的地质氮（N）和碳（C）循环是评估这些挥发性物质在固体地球（核心，地幔和地壳），海洋和大气之间的分布的基础。这份有关地球N和C循环的特别交流所载资料与对行星进化专题集合“阅读同位素和元素测量中的地球行星进化”感兴趣的研究人员有关。在这些主要储层之间，随着地质时间的变化，N和C的通量变化会影响其演化并确定地球大气的独特组成。在这里，我们回顾了N和C循环的几个关键地质方面，在过去的十年中，通过基于野外的，实验和理论研究，我们对这些方面的理解有了显着的进步。俯冲带是氮和碳从地球表面进入深层地球的最重要途径。通量量化中的一个关键问题是，有多少挥发性元素存储在下降的平板中并引入地幔中，有多少通过电弧岩浆作用返回到地面和大气中。对于N，保留的N为矿物中的\（\ text {NH} _ {4} ^ {+} \）对储层之间的通量有重大影响。\（\ text {NH} _ {4} ^ {+} \）的温度相关稳定性含矿物质决定了氮主要保留在板中至地幔深度（在地热梯度低的俯冲带中）还是脱挥发分（在地热梯度高的俯冲带中）。有几条证据表明，随着时间的推移，俯冲的N净流入，地幔正在向N放气，但是这个问题一直存在争议，相反的证据也存在。尽管如此，已经达成共识，行星N的大部分预算都存储在地球的地幔中，而大陆壳也构成了重要的N储层。对于C，从俯冲板中释放出来是通过脱碳反应，溶解和形成碳酸盐液体而发生的，但是板中或前臂地幔楔中C的再沉淀可能会限制C直接返回大气的有效性。碰撞带造山带中通过区域变质作用释放的碳也可能对碳向大气中的释放产生深远的影响，并且已经达成共识，认为这些造山带是大气中CO的来源而不是下沉₂。在更短的时间尺度上，通过地幔衍生的岩浆与含C的乡村岩石的相互作用而发生的接触变质作用，以及由此导致的大量CH ₄和/或CO _2的释放与全球变暖事件有关。